The present invention relates generally to gas turbine engines, and more particularly to a method of increasing service intervals by increasing engine gas temperature limit margins.
Flowpath components deteriorate inside gas turbine engines during operation. As the components deteriorate, engine controls automatically make adjustments to meet engine power requirements. These adjustments increase flowpath gas temperatures. New engines typically have gas temperature margins to allow for temperature increases during use. However, after extended use, the temperature margin becomes sufficiently low that the engine must be serviced. To recover temperature margin, the engine is overhauled at a service facility. During the overhaul, various deteriorated and damaged engine components are replaced. Such overhauls are expensive and time consuming. It is envisioned that substantial savings could be achieved if the number and frequency of overhauls were reduced. Further, if overhauls could be delayed to coincide with scheduled facility or airframe maintenance or with replacement of life limited components within the engine, it is envisioned that substantial savings could be achieved.
Moreover, because life limited components are sometimes replaced sooner than necessary when the engine is overhauled to recover engine gas temperature margin, optimal use of the life limited components is not achieved. Replacing life limited components before their lives are entirely exhausted necessitates more components being used over the life of an engine which increases operating expenses. Maintaining spare components inventories to meet the more frequent replacement schedule further increases expenses. Thus, it is anticipated that recovering engine gas temperature margin without removing engines from service could provide a substantial savings.
Among the several features of the present invention may be noted the provision of a method of extending a useful serviceable life of a gas turbine engine by increasing a limiting exhaust gas temperature margin degraded by engine use without replacing engine hardware. The method includes adjusting at least one engine parameter selected from a first group of engine parameters including a nozzle area, and a rotor speed.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.